Preparation And Properties Of Dental Antibacterial Polymeric Materials Modified With Novel Polymerizable Quaternary Ammonium Salts

The development of resinous materials with antibacterial activity, which are more and more widely used in the dental clinic for replacement, has long been the goal of oral science. Unfortunately, the monomers which were usually used as dental materials don't have antibacterial ability. Quaternary ammonium salts(QAS) not only exhibt good bactericidal properties, but slao have some advantages over other antibacterial agents, including low toxicity, greater stability, low corrosivity and extended residence time of biological activity. In order to provide resin composites with inhibitory properties against subsequent recurrent caries and other oral diseases, the dental maerials with long-lasting antibacterial ability were prepared by immobilization of an antibacterial component in the resin matrix.In this thesis, two series of polymerizable QAS were synthesized and characterized by infrared spectroscopy(IR) and nuclear magnetic resonance(1H-NMR). The resin-based restoratives with antibacterial activity were prepared by ultraviolet(UV) induced photopolymerization, which was usually used in stomatology. The factors, such as initiating agent, coinitiator, which affect free-radical copolymerization, were studied and optimized. The degree of double bond conversion of resin system incomporated with crosslinking antibanterial monomer was 17% higher than the ones which containg non-cross linking monomer. It will be helpful for improving the mechanical properties of resin and reducing the residual monomer.To evaluate the bactericidal activity of the QAS monomers against oral pathogenic bacterium, the minimum inhibitory concentration(MIC) and the minimum bactericidal concentration(MBC) for several species and time-kill kinetics against Streptococcus mutans were determined. The cytotoxicity was measured by MTT method. DMAE-CB,MAE-DB and MAE-HB showed strong antibacterial activity. Time-kill curve showed that all cells were killed by 10min contact with 19.2μg/mL of DMAE-CB. MAE-DB gave 100% killing rate at 4*MBC against Streptococcus mutans within 10min, while all cells were killed after contact with MAE-HB for 30min. The concentration which caused 50% toxocity(ID50) of MAE-DB and MAE-HB for human gingival fibroblasts lies between 5-10μg/mL, which was similar with that of Bis-GMA, the usual dental matrix monomer.The chemical and physical properties of experimental resin specimens containing antibacterial monomers were investigated. Surface hardness of restorative resins raised with the increase of the monomer mass, while the antibacterial resins modified with crosslinked monomer have higher hardness than the ones with usual monomer. Water sorptions of all dental restorative resins were less than 40μg/mm3. The antibanterial activity of an copolymerization adhesive resin was investigated by confocal laser scanning microscope(CLSM) and scanning electron microscope(SEM). The modified dental materials could exert contact antibacterial activity via exerting detrimental effects on the growth and membrane integrity of S. mutans.